A hydrological framework to improve precision of Vital Signs metrics in the Appalachian highlands

Science Center Objects

Stream flow is a fundamental driver of ecological structure and function, but its influence on bioassessment measures is poorly understood. Although extreme flow conditions (e.g., floods and droughts) have long been known to play a central role in structuring stream communities, a mechanistic understanding of the linkages between flow variables, landscape and local physical characteristics, and stream biota is lacking. The goal of this research is to develop a hydrologic framework for assessing stream monitoring trends in Appalachian streams, thereby improving the sensitivity of biological condition measures to detect change due to anthropogenic stressors. The study will assess hydrologic responses of aquatic fish and macroinvertebrate communities, and will support the National Park Service “Vital Signs” Monitoring Program.

Shenandoah National Park (SNP) is a long narrow protected area located along the spine of the Blue Ridge Mountains of Virginia. The Park is known for its beauty and biological diversity and is considered a prime example of reference conditions in the mid-Atlantic Highlands. Water resources in SNP include over 1000 km of streams draining into the Chesapeake Bay via the Rappahannock, Potomac, and James Rivers, and consist almost entirely of headwater (i.e., ≤ 3rd order) streams. Although streams draining most of the park are considered perennial, reaches within many of them are known to dry periodically during summer base-flow conditions. Streamflow in SNP is largely driven by precipitation and groundwater; snowmelt typically represents a minor component of surface flow. Moreover, groundwater inputs are primarily limited to those contained within shallow (0–9 m thick) layers of residuum and colluvium that overlie bedrock.

Our research will utilize retrospective analyses of long-term biological and flow data combined with new data and analyses of stream and watershed geomorphology to assess flow effects on stream bioassessment indices. Our project goals will be met through the four research objectives:

  1. Evaluate long-term annual variability in BMI and fish data collected in SNP as it relates to stream flow and flow disturbance history.
  2. Determine the geomorphic and hydrologic setting at long-term ecological monitoring (LTEM) sites in SNP.
  3. Develop biological response models that account for spatial and temporal flow variability to assess trends in biological condition as they relate to observed long-term (>20-years) patterns in water temperature (sensu climate change) and water quality in SNP.
  4. Develop tools to incorporate flow models into NPS trend analyses and reporting protocols.
Hydrological framework

Hydrological framework research.

(Credit: Craig Snyder, USGS Leetown Science Center. Public domain.)